The present invention relates to a piezoelectric component, such as a surface acoustic wave (SAW) device and a piezoelectric thin film filter used in a SAW duplexer and SAW filter, to be used in mobile communication devices such as a mobile phone. In particular, the invention relates to a piezoelectric component in which a piezoelectric device is on a wafer at a wafer-level, is packaged in a chip size, and a mesh-shaped member is seal-enclosed in a ceiling layer that constitutes a hollow section, and molding pressure resistance of the hollow section is improved by using a photosensitive resin film having a mica filer added thereto.
In a piezoelectric component (SAW device) equipped on a mobile phone, it is necessary to ensure a space, within which electrodes are oscillated due to a piezoelectric effect, by providing a predetermined hollow section around a comb electrode section (Interdigital Transducer Section herein after called as “IDT”). Conventionally, in order reduce the size of a SAW device, a SAW device chip is flip-chip bonded (face-down bonded) on a wiring substrate with use of a gold (Au) bump or solder bump, and the entirety of the SAW device chip is sealed with a resin or the like, to thereby configure a small size package device of a SAW device.
Furthermore, there has been proposed a microminiaturized chip-size package SAW device in which, in order to reduce the size and height of a SAW device, a predetermined hollow section is formed around comb electrode sections, the entirety of an aggregate piezoelectric substrate (wafer) on the comb electrodes side is sealed with a resin while retaining this hollow section, and having formed external connection electrodes, it is divided, by means of dicing, into individual SAW devices.
For example, in the SAW device disclosed in Patent Document 1 (Japanese Unexamined Patent Publication No. 2006-108993), a clearance (hollow section) formation layer (outer periphery wall) composed of a photosensitive resin is formed on the upper surface of a SAW chip (piezoelectric substrate), on which comb electrodes are formed, and a sealing layer (ceiling section) is laminated and sealed on this clearance formation layer, to thereby form a clearance (hollow section) around the comb electrodes.
Moreover, in the SAW device disclosed in Patent Document 2 (Japanese Unexamined Patent Publication No. 2006-197554), a cover having through electrodes is joined and sealed via a metallic joint section so as to face the SAW chip (piezoelectric substrate) having comb electrodes formed thereon, and a hollow section is formed between the SAW chip and the cover to accommodate the comb electrodes.
However, when mounting this type of a piezoelectric component on a mount substrate and modularizing it on site by means of transfer molding, normally, a pressure ranging from 5 MPa to 15 MPa is applied. Consequently, in a case where the clearance (hollow section) formation layer and the sealing layer of the SAW device disclosed in Patent Document 1 (Japanese Unexamined Patent Publication No. 2006-108993) are configured only with organic materials, there is a possibility that the hollow section that accommodates the comb electrodes therein may be contracted and the electrical characteristic of the comb electrodes may consequently be deteriorated in some cases when resin-sealing by means of transfer molding or the like, unless the thickness of the sealing resin layer that constitutes the ceiling section is increased or is configured with a hard material. However, it is extremely difficult to increase the thickness of the sealing resin layer, and configure the sealing resin layer with a hard material to thereby achieve molding pressure resistance, only with the photosensitive resin material used for this type of resin sealing.
Moreover, in the SAW device disclosed in Patent Document 2 (Japanese Unexamined Patent Publication No. 2006-197554), separate electrodes are required for forming through holes, in which through electrodes are to be provided, in a cover, and for joining and laminating a SAW chip (piezoelectric substrate) and the cover (substrate). Also there is a possibility that the substrates may be bent when laminating the substrates in some cases. Moreover there is a possibility that the cost of manufacturing piezoelectric components may increase in some cases as a result of laminating substrates (wafers) composed of the same material (piezoelectric substrate). Furthermore, in order to achieve reduction in the height of a piezoelectric component, the substrate (wafer) needs to be made thin. However, this has been extremely difficult to achieve.